Thanks!

Some basic mirroring is already included - you can use Transform/Mirror to create a mirror. It is also possible to select the mirrored object, and you can enable history on it (Edit/History) to cause the mirrored object to update when you manipulate the original.

In the future I do plan to add more in-depth support for symmetry, but it will be a while probably a version 2.0 or later feature.

- Michael